Update : Just try quickbms script for Persona 5 (http://aluigi.altervista.org/bms/persona5.bms).
Just "work" on the system.rdb ( and btw system.rdb.bin ) file.
I got a lot of random files (about 2 thousands) name like this "1cd00000@2447e8a" without extension :
@coolguyfire
Actually, i'm thinking about a way to translate in english or french it. I try your Unpack software with my lastest keys dump on my switch but look's like won't work bc of game size. A .tik story...
But look's like @coolguyfire extracted some file, i asked him for getting a copy and have a look...